Host Fishes and Conservation Status of Alasmidonta marginata (Bivalvia: Unionidae) in Minnesota

We examined laboratory host suitability and assessed the distribution and status of Alasmidonta marginata (Elktoe) in Minnesota. Of the 85 fish species tested, glochidia metamorphosed on 27 species in 6 families (Cyprinidae, Catostomidae, Fundulidae, Poeciliidae, Gasterosteidae, and Cottidae). All catostomid species facilitated metamorphosis, and overall, Catostomidae produced more juvenile mussels per fish. This result, in combination with a previous finding of naturally infested fish, suggests that catostomids are an important host for A. marginata in nature. From extensive surveys, we found extant populations of A. marginata in the St. Croix River, Upper Mississippi River, and Minnesota River systems. Alasmidonta marginata is apparently extirpated or its range has decreased in several interior Minnesota watersheds and the Mississippi River main stem. Barrier waterfalls and habitat degradation have influenced A. marginata's historic and recent distribution more so than the range of its hosts. Further study of naturally occurring and laboratory hosts for A. marginata and other Alasmidonta species is needed in order to improve conservation efforts and elucidate phylogenetic relationships for this group of mussels.